1. Field of the Invention
The present invention relates to an optical pick-up apparatus, and particularly to an optical pick-up apparatus having a plurality of semiconductor laser sources, etc., and to the structure of an optical disk apparatus.
2. Description of the Related Art
When a spherical lens is used as an optical pick-up collimator lens, two or three lenses are needed, however, when a non-spherical lens is used instead, only one lens is needed. Further, since resin is now shown to have properties suitable for formation of a lens, a non-spherical lens made of resin is now commonly used for a collimator lens, thereby allowing the suppliers' optical products to meet their need for reduction in size, weight, and cost of the products.
However, it has been shown that the temperature difference between a lens and its surroundings produces a temperature gradient across the lens and then causes lens distortion, and in general, the lens distortion of a lens made of resin is greater than that of a lens made of glass. For example, heat from a heat source provided on an optical base causes significant distortion in a collimator lens and such distortion leads to a problematic situation where recording or reproduction of information on or from a recording medium is not normally performed.
Generally, if it is possible to give wider spacing between a collimator lens and a heat source on an optical base or provide an optical base with the ability to efficiently dissipate heat, the problem associated with the heat generation arising as described above is not so serious. However, in a compact and thin optical pick-up apparatus intended to be incorporated into a notebook personal computer (PC), it is difficult to give wider spacing between a collimator lens and a heat source on an optical base or provide an optical base with the ability to efficiently dissipate heat. Further, in an optical pick-up apparatus comprising CD, DVD, HD-DVD laser diodes which emit light beams of three different wavelengths, the number of heat sources increases and space available for optical components is limited, and therefore, the conditions of heat dissipation, which are preferred as described above, are more difficult to be satisfied.
[Patent Document 1]
Japanese Patent Unexamined Publication No. 2004-133963
[Patent Document 1]
Japanese Patent Unexamined Publication No. 2003-45059
[Patent Document 1]
Japanese Patent Unexamined Publication No. 2002-319167